Gesundheit Again

By Medical Discovery News

June 12, 2015

Person sneezing

Have you ever noticed that many times sneezes come in threes? Repeated sneezes may be your body’s efforts to get rid of irritants in the nose when the initial sneeze is not strong enough to do so.

Sneezing has different meanings in cultures around the world. The Athenian General Xenophon gave an encouraging speech to his army that went on for an hour until a soldier sneezed. Taken as a favorable sign from the gods, the army proceeded to attack the Persians, but was ultimately defeated and the general killed. One of the Pagan beliefs is that sneezing opened one’s body to Satan or evil spirits, which is how the common response “Bless You” arose. In fact, Pope Gregory VII made the short prayer “May God Bless You” a required response to a sneeze as protection from the Black Plague. As you can see, the sneeze has often been misinterpreted in history.

The sneeze can be divided into two phases. The first phase, called the nasal or sensitive phase, results from a chemical or physical irritation of the tissue lining the nose called the nasal mucosa. This signal is transmitted through nerves to the sneezing center of the brain in the lateral medulla. The second phase begins once a sufficient number of nerves are stimulated. This is when the eyes shut, a deep breath is taken, and the opening between the vocal chords closes, increasing lung pressure to allow an explosive release of air through the mouth and nose. The purpose of the sneeze is to dislodge the irritant from the nose, since an estimated 40,000 microscopic particles are expelled by a sneeze. The speed of a sneeze is estimated to be between 135 and 950 feet per second, or up to 85 percent of the speed of sound.

Allergies, infections, and inflammation of the nose’s mucous membrane (rhinitis) can trigger fits of sneezing. Allergies are the result of an immune response to substances in the environment that do not bother most people, like pollen, pet dander, or bee venom. People with allergies mount an immune response to those substances including the inflammation, which again irritates the nasal passages and causes sneezing. When you have a virus like the cold or flu, the immune response also causes inflammation of the nasal passages, which irritates the nerve endings and leads to the familiar itching and sneezing.

The sneeze is also a way for the body to reboot the environment in the nose, so the nasal mucosa can once again trap particles we breathe in from the environment. Sneezing more than once in a row is often an attempt to eject whatever is irritating the nasal passages when the first sneeze was not successful. This explains why people suffering from allergies sneeze more often, since the allergen they are trying to expel is still around. Other people who routinely sneeze many times in a row may just not have forceful sneezes.

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How Clean is Too Clean?

Oct. 31, 2014

By Medical Discovery News

Cleaning supplies

Common knowledge and previous studies generally agree that children who grow up in the inner city and are exposed to mouse allergens, roach allergens, and air pollutants are more likely to develop asthma and allergies. But a recent study adds a new twist – children exposed to these substances in their first year of life actually had lower rates of asthma and allergies. However, if these allergens were first encountered after age one, this protective effect did not exist.

Another study parallels this one, concluding that children growing up on farms also have lower allergy and asthma rates. Scientists argue that farm children are regularly exposed to microbes and allergens at an early age, leading to this same protective effect.

Asthma is the most common chronic condition among children. One in five Americans, or 60 million people, has asthma and allergies. In the industrialized world, allergic diseases have been on the rise for more than 50 years. Worldwide, 40-50 percent of school-age children are sensitive to one or more common allergens.

In this study, scientists enrolled 467 children from the inner cities of Baltimore, Boston, New York City, and St. Louis and followed their health since birth. The infants were tested for allergies and wheezing by periodic blood tests, skin-prick tests, and physical exams, and their parents were surveyed. They also sampled and analyzed the allergens and dust in the homes of over 100 of the subjects.

Children who lived in home environments that included cat and mouse dander as well as cockroach droppings in their first year of life were much less likely to develop wheezing or allergies when compared to children who were not exposed to these substances. This protective effect was additive, so children exposed to all three were less likely to develop wheezing compared to children exposed to two, and those children were more protected than those who were exposed to only one. Only 17 percent of children who lived in homes with all three allergens experienced wheezing by age three, compared to 51 percent of children who lived in homes without such allergens. Interestingly, dog dander did not have a protective effect against the development of allergies or wheezing.

The richness of the bacterial populations children were exposed to enhanced this protective effect. This suggests that household pests may be the source of some of the beneficial bacteria in the inner city environment. Early exposure to allergens and certain bacteria together provide the greatest effect.

An infant’s microbiome, the total makeup of bacteria in and on their bodies, is developed during their first year of life. The bacteria colonizing an infant’s gastrointestinal system affects their immune system and influences the development of allergies. Scientists hypothesize that something similar may be happening in the airways and lungs, as kids with asthma have altered bacterial populations in their respiratory systems.

There is mounting evidence exposures to allergens and bacteria in the first few months of life help shape the respiratory health of children. But we don’t yet know how specific allergens and bacteria induce this protective effect, or how they can be used to treat children and reduce their chances of developing allergies and asthma.

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An Itchy Situation

Nov. 1, 2013

By Medical Discovery News

Anyone ever bitten by a mosquito can attest to its itchy consequences. New research has discovered just how our bodies detect and process itching, leading to a better understanding of our reaction to itching and hopefully better treatments for it.

The clinical term for an itch is pruritus, and at least 16 percent of people experience an itch that just doesn’t go away. The most common dermatological complaint, long-term itching can be caused by chronic renal disease, cirrhosis, some cancers, multiple sclerosis, diabetes, shingles, allergic reactions, drug reactions, and pregnancy.

Prolonged itching and scratching can increase the intensity of the itch, possibly leading to neurodermatitis, a condition in which a frequently scratched area of skin becomes thick and leathery. The patches can be raw, red, or darker than the rest of the skin. Persistent scratching can also lead to a bacterial skin infection, permanent scars, or changes in skin color. The super strong pain reliever morphine can cause such a severe whole-body itch that some patients choose to forgo it and live with the pain.

Sensory neurons called TRPV1 cells detect itchy substances on skin. TRPV1 cells have long nerve fibers that extend into skin, muscle, and other tissues to help monitor conditions. It has not been clear how these neurons sort through different sensations like pain and temperature and route the signal along the proper pathway to the appropriate area of the brain for perception.

New research has revealed a small group of those neurons produce a substance called natriuretic polypeptide b (Nppb), a hormone known to be involved in regulating the heart. Surprisingly, when Nppb is produced by TRPV1 cells it acts as a neurotransmitter, a chemical messenger secreted by neurons to carry, boost, and control signals between neurons and other cells.

When scientists genetically modified mice to eliminate Nppb, they did not itch. Nppb binds to a specific receptor called Npra on particular nerves in the spinal column. When those cells were eliminated in mice, again, they did not itch. Interestingly, removing these cells did not impact other sensory sensations such as temperature, pain, and touch.

A similar transmission presumably exists in humans, but that has not yet been determined. Knowing which molecules and cells are involved will help scientists study how humans perceive itch signals. Before these findings, scientists thought a molecule called gastrin releasing peptide was responsible for transmitting the itch signal from nerves, and that itching was a low level form of pain.

Understanding the itch signaling pathway offers the opportunity to create drugs that specifically block that signal and alleviate unpleasant and chronic itching with fewer side effects.

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